Presently, there is a wide variety of motion simulators adaptable to various applications that are commercially available. These simulators allow the human brain to experience apparent motion by a combination of momentary movements. To achieve this simulation of movement, the simulators are varied in structure and arrangement. There are six degrees of freedom systems primarily used for simulating the flying characteristics of aircraft. With six degrees of freedom, the simulator is capable of moving in three linear directions and three angular directions singularly or in any combination. The six degrees of freedom are commonly referred to as pitch, roll, yaw, surge, sway and heave. One such prior art motion simulator system introduced in 1965 is known as a "Stewart platform." For many applications, six degrees of freedom are not needed.
There are also simplified three or four degrees of freedom systems typically utilized for simulating less sophisticated aircraft and ground vehicles. These simplified motion simulators are also utilized in 3-D games and movement simulators typically found in arcades. Compared to six degrees of freedom systems, the three degrees of freedom systems, for example, only permit movement for simulating pitch, roll and heave.
However, these known motion simulation systems are often plagued by geometrical complexities. Therefore, these systems are difficult to design and manufacture without complicated arrangements. These complications typically include interference between extendable members that provide movement such as lift. The extendable members also provide stability to the motion simulation system.
Typically, the extendable members are conventional hydraulic actuators having a cylinder housing, plunger and piston. The piston is mounted on the bottom end of the plunger and is sized for being received into the cylinder housing. The plunger is slidingly engaged to the cylinder housing and is selectively raised and lowered in the cylinder housing in response to controlled pressure via a hydraulic system.
Although the three degrees of freedom systems drastically reduce the number of complications compared to the six degree of freedom systems, there is room for improvement in the design of these known motion simulators. For example, the number of parts can be reduced and the range of movement required for creating a desired effect can be narrowed. Reducing both the number of parts and the range of motion required to effectively operate the simulators prolongs their life while also reducing their manufacture and maintenance costs.
For example, a great number of commercially available simulators have actuators which are crossed in a complicated manner that interfere with one another. Each crossed actuator has a limited range of motion due to the proximity of the adjacent actuator. Alternatively, the actuators may be positioned in a substantially upright or vertical manner. Vertically-oriented actuators have a broader range of motion because there is no possibility of interfering with an adjacent actuator. Another advantage associated with vertically-oriented actuators is that the movement of the simulator created in response to actuating the vertically-oriented actuators is more efficient. The crossed actuators have to extend further to create the same movement that vertically-oriented actuators can create with less of an extension. Because the upright actuators can be smaller, the hydraulics necessary to operate the actuators maybe simplified. Therefore, a more direct simulated movement is created in response to movement of the vertically-oriented actuators with a more economical and easily manufactured motion simulator.
A motion simulator supported by only upright actuators at each corner is uncontrollable because it is capable of six degrees of freedom. However, this six degrees of freedom system can be controlled by permitting only three degrees of freedom. Without supports to maintain the vertically-oriented actuators in an upright manner, a six degrees of freedom system will collapse. Furthermore, when the plunger of an actuator is raised in the cylinder housing, the shear forces created by the movement of the simulator allow the cylinder housing and plunger to flex. This undesirable flexing motion creates unrealistic movement and exposes the actuator to excessive wear. Therefore, the amount of heave that vertically-oriented actuators are allowed to create is limited by the shear forces acting upon them.
In response to the realized inadequacies of these earlier motion simulators, it became clear there is a need for a more efficient and simplified motion simulator. This simplified motion simulator must have substantially vertically-oriented actuators that power the motion simulator by providing motion to the simulator, but which do not themselves stabilize the motion simulator. Therefore, this novel motion simulator must also provide a stabilizing system that maintains the actuators in an upright position, prevents the flexing of extended actuators, but which allows vertical translation in both directions.